redis持久化問題處理

這個是最近在開發的過程中遇到的問題，因為需要頻繁使用redis作為中間查詢操作，突然故障了，服務中止，然后拋出異常

2020-01-09 09:34:17.848 ERROR 25703 --- [ XNIO-2 task-83] o.z.p.spring.web.advice.AdviceTrait      : Internal Server Error

org.springframework.data.redis.RedisSystemException: Error in execution; nested exception is io.lettuce.core.RedisCommandExecutionException: MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:54)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:52)
    at org.springframework.data.redis.connection.lettuce.LettuceExceptionConverter.convert(LettuceExceptionConverter.java:41)
    at org.springframework.data.redis.PassThroughExceptionTranslationStrategy.translate(PassThroughExceptionTranslationStrategy.java:44)
    at org.springframework.data.redis.FallbackExceptionTranslationStrategy.translate(FallbackExceptionTranslationStrategy.java:42)
    at org.springframework.data.redis.connection.lettuce.LettuceConnection.convertLettuceAccessException(LettuceConnection.java:257)
    at org.springframework.data.redis.connection.lettuce.LettuceHashCommands.convertLettuceAccessException(LettuceHashCommands.java:445)
    at org.springframework.data.redis.connection.lettuce.LettuceHashCommands.hSet(LettuceHashCommands.java:70)
    at org.springframework.data.redis.connection.DefaultedRedisConnection.hSet(DefaultedRedisConnection.java:827)
    at org.springframework.data.redis.connection.DefaultStringRedisConnection.hSet(DefaultStringRedisConnection.java:501)
    at org.springframework.data.redis.core.DefaultHashOperations.lambda$put$8(DefaultHashOperations.java:178)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:224)
    at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
    at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:95)
    at org.springframework.data.redis.core.DefaultHashOperations.put(DefaultHashOperations.java:177)
    at com.smpteam.aaaa.service.impl.RedisServiceImpl.setESSession(RedisServiceImpl.java:59)
    at com.smpteam.aaaa.service.impl.RedisServiceImpl$$FastClassBySpringCGLIB$$11b51629.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    . . .
Caused by: io.lettuce.core.RedisCommandExecutionException: MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

然后我通過redis-cli登錄redis服務器檢查情況，發現ping不通

(error) MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.
這提示及其友好，雖長但我喜歡：）

Redis問題

MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.

Redis被配置為保存數據庫快照，但它目前不能持久化到硬盤。用來修改集合數據的命令不能用。請查看Redis日志的詳細錯誤信息。

原因

強制關閉Redis快照導致不能持久化。本質上是內存不足導致的。因此需要進行相關的內存處理：

1. 修改redis config
2. 修改快照備份的目錄，即將快照重定向到其他目錄
3. 修改主機內存配置

解決方案1

將stop-writes-on-bgsave-error設置為no，這個方式是直接關閉保存持久化快照

127.0.0.1:6379> config set stop-writes-on-bgsave-error no

這個在生產中可能會出現一些問題，這個然而這個方法治標不治本，他只是讓我們“忽略”他而已，使用之前需要確認bgsave失敗的原因，比如當redis用于緩存、會話的場景的時候，這么做是允許的

解決方案2

將備份的rdb文件，重定向到目錄

CONFIG SET dir /tmp/some/directory/other/than/var
CONFIG SET dbfilename temp.rdb

使用這個命令之后，需要確保bgsave_in_progress返回結果是0

解決方案3

在內核運行時動態地修改內核的運行參數

echo 'vm.overcommit_memory = 1' >> /etc/sysctl.conf
sysctl vm.overcommit_memory=1